Adapting Transfer Rate of Cached Data to Prevent Stoppage of Data Transmission

1. A method for adapting a transfer rate of cached data in a file system controlling access to a tape library comprising: receiving, at the file system, a request to access the tape library; estimating, by the file system, a first data transfer rate from an anticipated tape library operation completion duration and from a capacity of cached data to be transmitted from a cache of the file system; initiating access to the tape library; and adapting the first data transfer rate to a second data transfer rate to transmit the capacity of the cached data throughout the anticipated tape library operation completion duration.

2. The method according to claim 1 , wherein adapting the first data transfer rate to a second data transfer rate further comprises: updating the first data transfer rate with the second data transfer rate.

3. The method according to claim 1 , wherein adapting the first data transfer rate to a second data transfer rate further comprises: determining remaining capacity of the cached data.

4. The method according to claim 3 , wherein the first data transfer rate is updated in response to the determined remaining capacity of the cached data indicating at least 75% utilization of the cache so that when the remaining capacity of the cached data falls below 75%, the first data rate is updated to modify the remaining capacity of the cached data with respect to a remaining data capacity and an estimated positioning time which is estimated at each respective step, while when the remaining capacity of the cached data reaches 75%, the remaining capacity of the cached data is corrected with respect to an updated remaining data capacity and a current estimated position time.

5. The method according to claim 1 , wherein adapting the first data transfer rate to a second data transfer rate further comprises: initiating access to archived data in the tape library and determining whether positioning of tape within a tape cartridge is completed; retrieving archived data when it has been determined that the tape has been cued; and switching smoothly from the transmission of cached data to the transmission of archived data subsequent to transmission of the capacity of the cached data.

6. The method according to claim 1 , wherein adapting the first data transfer rate to a second data transfer rate further comprises: changing the transmission of cached data to archived data retrieved from the tape library without stopping data transmission.

7. The method according to claim 1 , wherein the anticipated tape library operation completion duration is an estimated time calculated as the sum of: a duration of unloading a first cartridge and moving the first cartridge from a drive to a first slot within the tape library; a duration of moving and loading a second cartridge from a second slot to the drive; and a tape positioning duration for positioning a target file in the loaded cartridge.

8. A non transitory computer program product comprised within a file system configured to control access to a tape library and adapt a data transfer rate of cached data, the computer program product comprising program instructions that are stored on a non-transitory computer readable storage medium and when executed cause the file system to: receive a request to access the tape library; estimate a first data transfer rate from an anticipated tape library operation completion duration and from a capacity of cached data to be transmitted from a cache; initiate access to the tape library; and adapt the first data transfer rate to a second data transfer rate to transmit the capacity of the cached data throughout the anticipated tape library operation completion duration.

9. The computer program product of claim 8 , wherein the program instructions to adapt the first data transfer rate to a second data transfer rate further cause the file system to: update the first data transfer rate with the second data transfer rate.

10. The computer program product of claim 8 , wherein the program instructions to adapt the first data transfer rate to a second data transfer rate further cause the file system to: determine remaining capacity of the cached data.

11. The computer program product of claim 10 , wherein the first data transfer rate is updated in response to the determined remaining capacity of the cached data indicating at least 75% utilization of the cache so that when the remaining capacity of the cached data falls below 75%, the first data rate is updated to modify the remaining capacity of the cached data with respect to a remaining data capacity and an estimated positioning time which is estimated at each respective step, while when the remaining capacity of the cached data reaches 75%, the remaining capacity of the cached data is corrected with respect to an updated remaining data capacity and a current estimated position time.

12. The computer program product of claim 8 , wherein the program instructions to adapt the first data transfer rate to a second data transfer rate further cause the file system to: initiate access to archived data in the tape library and determine whether positioning of tape within a tape cartridge is completed; retrieve archived data when it has been determined that the tape has been cued; and switch smoothly from the transmission of cached data to the transmission of archived data subsequent to transmission of the capacity of the cached data.

13. The computer program product of claim 8 , wherein the program instructions to adapt the first data transfer rate to a second data transfer rate further cause the file system to: change the transmission of cached data to archived data retrieved from the tape library without stopping data transmission.

14. The computer program product of claim 8 , wherein the anticipated tape library operation completion duration is an estimated time calculated as the sum of: a duration of unloading a first cartridge and moving the first cartridge from a drive to a first slot within the tape library; a duration of moving and loading a second cartridge from a second slot to the drive; and a tape positioning duration for positioning a target file in the loaded cartridge.

15. A system for adapting a transfer rate of cached data, the system comprising: a tape library to selectively load and unload a plurality of cartridges from a plurality of slots to a drive for transmitting to the file system archived data retrieved from a particular cartridge; and a file system to control the tape library, the file system comprising a cache and configured to receive a request from a requestor to access the tape library; estimate a first data transfer rate from an anticipated tape library operation completion duration and from a capacity of cached data to be transmitted from the cache to the requestor; initiate access to the tape library; and adapt the first data transfer rate to a second data transfer rate to transmit the capacity of the cached data to the requestor throughout the anticipated tape library operation completion duration.

16. The system claim 15 , wherein file system is further configured to update the first data transfer rate with the second data transfer rate.

17. The system claim 15 , wherein file system is further configured to determine remaining capacity of the cached data.

18. The system claim 17 , wherein the first data transfer rate is updated in response to the determined remaining capacity of the cached data indicating at least 75% utilization of the cache so that when the remaining capacity of the cached data falls below 75% , the first data rate is updated to modify the remaining capacity of the cached data with respect to a remaining data capacity and an estimated positioning time which is estimated at each respective step, while when the remaining capacity of the cached data reaches 75%, the remaining capacity of the cached data is corrected with respect to an updated remaining data capacity and a current estimated position time.

19. The system of claim 15 , wherein file system is further configured to: initiate access to archived data in the tape library and determine whether positioning of tape within a tape cartridge is completed; retrieve archived data when it has been determined that the tape has been cued; and switch smoothly from the transmission of cached data to the transmission of archived data subsequent to transmission of the capacity of the cached data.

20. The system of claim 15 , wherein the anticipated tape library operation completion duration is an estimated time calculated as the sum of: a duration of unloading a first cartridge and moving the first cartridge from a drive to a first slot within the tape library; a duration of moving and loading a second cartridge from a second slot to the drive; and a tape positioning duration for positioning a target file in the loaded cartridge.